Case: E.max Inlay on Tooth #30, Female Patient with Chipping Composite
Patient Background
- Age: 34 years old
- Chief complaint: "My filling keeps chipping when I eat anything crunchy on the left side."
- Tooth: #30 (mandibular left first molar)
- History: The tooth had a large MO composite placed three years earlier. The composite had chipped twice in the past year, most recently two weeks before this case. The patient said she could feel a rough edge with her tongue and was getting nervous about the tooth breaking further.
- Clinical findings on the scan: Both buccal and lingual cusps were intact. The old composite extended into the central groove but did not involve the cusps. Margins were supragingival mesially and equigingival distally. No cracks visible on the digital scan. Pulp test positive (vital tooth).
What the Dentist Requested
The referring dentist wanted a bonded ceramic restoration that would outlast the composite and match the adjacent teeth. He specified:
- E.max inlay (lithium disilicate)
- Shade A2, matched to tooth #29
- Standard turnaround (no rush)
- Note on the Rx: "Patient is tired of having this re-done. Wants something durable."
How We Built It
Design decisions. We kept the preparation conservative — an inlay, not an onlay, because both cusps were sound and the isthmus was narrow. The key rule: if a cusp is covered, the restoration is an onlay, not an inlay. This case stayed intracoronal. Minimum occlusal thickness was set at 1.5 mm in the central fossa to give the ceramic enough body to resist fracture under load, following the preparation guidelines in Evidence-based concepts and procedures for bonded inlays and onlays, Part II. Internal line angles were rounded in CAD to reduce stress concentration. Margins were designed as butt joints with no bevel, because a butt margin seats cleaner and is easier to finish at the chair.
Material and milling. We used an IPS e.max CAD block in shade A2, HT (high translucency). The block was milled in the blue state, then crystallized in our programmable furnace on a locked firing cycle — 850°C for 7 minutes under vacuum, per the manufacturer's protocol. After crystallization the inlay was glazed once, and the occlusal surface was lightly polished to reduce wear on the opposing tooth.
Bonding surface preparation. The intaglio (fitting surface) was etched with 5% hydrofluoric acid for 20 seconds, rinsed thoroughly, dried, and treated with a silane coupling agent. The bonding protocol for lithium disilicate is well documented: the all-ceramic bonding guide and the luting protocol for lithium disilicate and zirconia both emphasize that HF etching and silane are non-negotiable for glass ceramics like E.max. We packaged the inlay with the etched surface protected by a plastic cap so it would arrive at the clinic in bonding-ready condition. A printed instruction card went into the box reminding the dentist to use a resin cement and to avoid any try-in paste that could contaminate the silane layer.
Quality checks before shipping. We verified the margin seal under 10× magnification, checked the proximal contact on a printed working model (snug, not binding), and confirmed occlusal clearance against the opposing scan. The inlay was photographed from four angles and the images were attached to the shipping email, so the dentist could see what was coming before it arrived.
Patient and Dentist Feedback After Try-In
At try-in (same week). The dentist reported the inlay seated fully on the first attempt with no adjustments needed. The patient said the tooth felt smooth and the bite felt even. No sensitivity during the bonding procedure. The dentist bonded it with a dual-cure resin cement, removed the excess, and light-cured per the cement manufacturer's instructions.
Two weeks later. The patient called the clinic to say the tooth felt "completely normal" and she had been eating almonds and apples on that side with no discomfort. The dentist sent us a follow-up note: "She's very happy. No post-op sensitivity, no high spots. This is exactly what she needed after two failed composites."
Three months later (voluntary follow-up). The patient was in for a routine hygiene visit. The hygienist checked the inlay and found the margins clean, no staining, and no secondary caries on probing or radiograph. The patient said she had forgotten which tooth had the restoration because it felt identical to her other molars.
Why This Case Worked
Three things lined up: the preparation gave us the thickness we needed, the material matched the load and the space, and the bonding surface was prepped correctly before it left the lab. The clinical literature on bonded ceramic inlays shows survival rates around 90–95% at five years and 85–91% at ten years, with fracture as the dominant late failure mode. Fracture risk drops when the ceramic is thick enough and the bond is chemically sound — both of which are controllable from the lab side.
What we can't control is the clinical environment after the inlay is seated, but we can make sure the three things on our side — thickness, material choice, and surface prep — are correct before the case leaves the building.
How We Handle Molar Inlay and Onlay Cases
Every molar case starts the same way: we read the scan, read the prescription, and check whether the two match. If they don't, we say so before we start any fabrication.
What we check on every case:
What we check | Why it matters |
|---|---|
Tooth number, pulp status (vital / post-endo), and remaining walls | A post-endo molar with major tissue loss is a different design conversation than a vital molar with an MO defect. |
Whether cusps are involved | If a cusp is covered, the restoration is an onlay, not an inlay. The design, thickness, and bonding plan all change with that designation. |
Occlusal clearance and interocclusal space | Lithium disilicate needs a minimum thickness to resist fracture. If the space isn't there, we propose a different material or a design change. |
Signs of parafunction or heavy wear on adjacent/opposing teeth | Parafunction raises the risk bar on any bonded ceramic. Material and thickness go up, and we say so in the design confirmation. |
Margin location and whether clean isolation for bonding is feasible | If a margin is deep subgingival with no clear isolation path, we hold the case and ask rather than guess. |
If anything on the scan contradicts the prescription, or the material choice doesn't fit the clinical situation, we contact the dentist the same day and propose an alternative before any milling starts.
Materials We Use for Molar Partial-Coverage Work
The in-house production covers CAD design, milling, zirconia sintering, glass-ceramic processing, PFM work, and digital model fabrication. Everything stays in one facility — no outsourcing to third-party labs. Materials are not interchangeable; each one asks different things of the preparation and the bonding workflow.
Material | Where it fits for molars | Minimum occlusal thickness we design to | Intaglio surface treatment |
|---|---|---|---|
Lithium disilicate (E.max) | Molar inlays with intact cusps, onlays with cusp coverage, post-endo molars with sufficient remaining structure. The aesthetic ceiling, strength in the middle band; thickness is non-negotiable. | 1.0 mm central fossa / 1.5–2.0 mm over covered cusps | 5% HF for ~20 s, silane, resin cement |
Monolithic multilayer zirconia | Full-coverage crowns, including redesigns from inlays where parafunction, thin space, or extensive cusp loss changes the picture. Strongest option we run. | Can tolerate thinner occlusal clearance than lithium disilicate | Air abrasion with 30–50 µm alumina, 10-MDP primer. No HF. |
PFM | Posterior full-coverage where strength and cost matter more than translucency. | — | — |
Nickel-free and beryllium-free options are available on request. Material composition sheets, batch certificates, and furnace logs for a given firing are available if your QA process needs them.
For a deeper read on where CAD/CAM ceramics sit mechanically and clinically, CAD/CAM Ceramic Restorative Materials for Natural Teeth covers the material families we use and their clinical performance data.
What Happens When a Case Doesn't Match the Prescription
Some cases should not be fabricated as written. When we see a mismatch between the scan and the prescription, we pause and contact the dentist before any fabrication starts.
Five situations where we hold the case:
Situation | Why we don't mill as submitted | What we propose instead |
|---|---|---|
A cusp is covered on the scan but the prescription says "inlay" | Mislabelled design leads to a mismatched bonding plan at the chair | Redesign as an onlay with cuspal coverage and matching bonding notes |
An endodontically treated molar with major tissue loss, "inlay" on the prescription | An intracoronal restoration doesn't protect against cuspal flexure | Onlay with cusp coverage, or a full-coverage crown if remaining structure is below the ferrule threshold |
Available interocclusal clearance is below the material's minimum thickness | Thin ceramic in a loaded area is a predictable fracture | A stronger material at the same thickness, or a design change to recover clearance |
Deep subgingival margin on the scan with no clear isolation path | Bonding workflow cannot be executed cleanly | Hold, ask the clinic for margin exposure or a different margin location |
Crack extending toward the pulp visible on the scan | The crack is the controlling factor, not the restoration | Hold the case, send the finding back to the clinic for a clinical call |
The case above (E.max inlay on #30) did not trigger any of these flags. When a case does, the dentist gets a message from us the same day with the reason and the proposed alternative, and nothing gets milled until we have written confirmation.
Turnaround, Revisions, and Quality Checks
Standard lab production time for a single-unit crown / inlay / onlay is 2–3 working days. Complex implant and full-arch work runs 5–7 working days. The clock starts when complete case data reaches us — digital scan or physical impression, opposing arch, bite registration, shade, and prescription. Working days only; weekends and public holidays don't count. Time spent waiting for missing files, design approval, or client replies does not count toward lab production time.
Design revisions: One initial design plus two free revisions per case. Design previews, screenshots, or STL files can be sent for approval before milling.
Pre-ship QC on every case: Edge seal under magnification, intaglio inspection, proximal contact on the printed working model, occlusal check against the opposing scan, and shade and surface verification against the submitted photos. If a pre-ship QC photo helps your workflow, we attach it to the shipping confirmation.
When a case comes back: We separate two categories upfront. If the issue can be adjusted intra-orally without touching the restoration body, margin, or seating, that's a chair-side adjustment. If it affects seating, margin seal, occlusion, retention, or biological safety, the case comes back and is reworked at no charge. On a rework, we open the original case file, pull the design and milling records, and run a root-cause review — the goal is to fix this case and to prevent the same cause from appearing on the next one.
What We Need to Start Your Case
Send these together and the case enters production the same working day:
- Case details: Tooth number, restoration type (inlay / onlay / crown), pulp status, and any notes on occlusion or parafunction.
- Digital scan or physical impression: Working jaw, opposing jaw, and bite registration. We accept VPS impressions, polyether, stone models, and 3D-printed resin models.
- Shade reference: A photo with the shade tab next to the prepped tooth is ideal. For thin ceramic, note the stump shade.
- Prescription: Clinic contact, dentist name, patient reference, material choice, and the date you need it back.
- Any constraints: Fixed occlusal clearance, a delivery deadline, or allergy flags (nickel-free or beryllium-free if required).
If anything is missing or unclear, we pause and ask the same day. We don't guess, and we don't fabricate partway hoping the missing detail doesn't matter.
Open a Case or Visit the Lab
Send a scan or impression with the intake above, and you'll get a design confirmation back before any milling starts. If we think the prescription should change, you'll get the reason and the alternative in the same message.
Factory visits in Shenzhen, production-line walk-throughs, and video inspections of the CAD/CAM and furnace workflow are open to dentists, clinics, and lab partners who want to see the production process in person.